[PATCH v1 05/21] target/cris: add BQL to do_interrupt and cpu_exec_interrupt

[Robert Foley <robert.foley@linaro.org>]

This is part of a series of changes to remove the implied BQL
from the common code of cpu_handle_interrupt and
cpu_handle_exception.  As part of removing the implied BQL
from the common code, we are pushing the BQL holding
down into the per-arch implementation functions of
do_interrupt and cpu_exec_interrupt.

The purpose of this set of changes is to set the groundwork
so that an arch could move towards removing
the BQL from the cpu_handle_interrupt/exception paths.

This approach was suggested by Paolo Bonzini.
For reference, here are two key posts in the discussion, explaining
the reasoning/benefits of this approach.
https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg08731.html
https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg00044.html

Signed-off-by: Robert Foley <robert.foley@linaro.org>
---
 target/cris/helper.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/target/cris/helper.c b/target/cris/helper.c
index 67946d9246..22aecde0f5 100644
--- a/target/cris/helper.c
+++ b/target/cris/helper.c
@@ -45,8 +45,10 @@ void cris_cpu_do_interrupt(CPUState *cs)
     CRISCPU *cpu = CRIS_CPU(cs);
     CPUCRISState *env = &cpu->env;
 
+    qemu_mutex_lock_iothread();
     cs->exception_index = -1;
     env->pregs[PR_ERP] = env->pc;
+    qemu_mutex_unlock_iothread();
 }
 
 void crisv10_cpu_do_interrupt(CPUState *cs)
@@ -128,6 +130,10 @@ void crisv10_cpu_do_interrupt(CPUState *cs)
     CRISCPU *cpu = CRIS_CPU(cs);
     CPUCRISState *env = &cpu->env;
     int ex_vec = -1;
+    bool bql = !qemu_mutex_iothread_locked();
+    if (bql) {
+        qemu_mutex_lock_iothread();
+    }
 
     D_LOG("exception index=%d interrupt_req=%d\n",
           cs->exception_index,
@@ -183,6 +189,9 @@ void crisv10_cpu_do_interrupt(CPUState *cs)
                   env->pregs[PR_CCS],
                   env->pregs[PR_PID],
                   env->pregs[PR_ERP]);
+    if (bql) {
+        qemu_mutex_unlock_iothread();
+    }
 }
 
 void cris_cpu_do_interrupt(CPUState *cs)
@@ -190,6 +199,10 @@ void cris_cpu_do_interrupt(CPUState *cs)
     CRISCPU *cpu = CRIS_CPU(cs);
     CPUCRISState *env = &cpu->env;
     int ex_vec = -1;
+    bool bql = !qemu_mutex_iothread_locked();
+    if (bql) {
+        qemu_mutex_lock_iothread();
+    }
 
     D_LOG("exception index=%d interrupt_req=%d\n",
           cs->exception_index,
@@ -265,6 +278,9 @@ void cris_cpu_do_interrupt(CPUState *cs)
           env->pregs[PR_CCS],
           env->pregs[PR_PID],
           env->pregs[PR_ERP]);
+    if (bql) {
+        qemu_mutex_unlock_iothread();
+    }
 }
 
 hwaddr cris_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
@@ -294,6 +310,7 @@ bool cris_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
     CRISCPU *cpu = CRIS_CPU(cs);
     CPUCRISState *env = &cpu->env;
     bool ret = false;
+    qemu_mutex_lock_iothread();
 
     if (interrupt_request & CPU_INTERRUPT_HARD
         && (env->pregs[PR_CCS] & I_FLAG)
@@ -315,6 +332,7 @@ bool cris_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
             ret = true;
         }
     }
+    qemu_mutex_unlock_iothread();
 
     return ret;
 }
-- 
2.17.1